Field
The present invention relates to a fuel cell system installed in a vehicle, a fuel cell vehicle, and a method for controlling the same.
Related Art
In some conventionally known fuel cell systems installed in a vehicle, required generated power of a fuel cell is calculated in accordance with an accelerator depression amount, and amounts of oxygen and hydrogen supplied to the fuel cell are controlled in such a manner that the power generated by the fuel cell matches the required generated power (JP-A-2011-15580). In the fuel cell system, when the required generated power of the fuel cell drops due to the deceleration of the vehicle or the like, required driving power of an air compressor that supplies oxygen to the fuel cell drops.
However, because the response of the air compressor is slow due to inertia, for example, when the required generated power sharply drops due to the sharp drop in the accelerator depression amount, oxygen is supplied to the fuel cell even after the required driving power drops to 0, until the compressor stops. Thus, there are a problem that dry up of the fuel cell occurs and a problem that excessively generated power leads to a lower fuel efficiency and over charging of a secondary battery. In view of the above, the present inventors have found out that the problems can be solved by performing such a control that the required driving power of the compressor drops at a higher drop rate than a drop rate of the required generated power when the required generated power sharply drops. However, when this control is performed, the required driving power drops to 0 before the required generated power does. Thus, the fuel cell might be unable to generate power due to the lack of oxygen after the compressor is stopped, and thus might fail to generate power corresponding to the required generated power. When this happens, there is a problem that the fuel cell system fails to supply the required power to a driving motor of the vehicle. As a result, the torque of the driving motor sharply drops, and thus what is known as torque shock occurs.